GDNF and renal agenesis: Renal agenesis results from defects in genes that regulate initial UB outgrowth such as Gdnf, Ret, and Gfra1. Also, the loss of certain genes, for example Eya1, Six1, Hox11, Wnt4, and Fgf8, which are involved later during metanephric development or nephron patterning, causes renal agenesis or hypoplasia [2].